Now to a story that pits TV stations, churches, audio engineers and Broadway theaters against the Federal Communications Commission. At issue are the wireless microphones that those diverse entities use and the broadcast frequencies they share - frequencies the FCC wants to sell. Cellular and other wireless data carriers are eager to buy them. The planned sale is being challenged in federal court because, as Rick Karr reports, broadcasters and others are worried that they won't be able to use the little mics that they now depend on.

RICK KARR, BYLINE: Rick Chinn remembers when wireless microphones were not reliable. In the mid-1970s, he was doing sound at a venue in Seattle for everything from Amway meetings to concerts by Henry Mancini, The Temptations and others. The venue owned a wireless mic.

RICK CHINN: People wanted to use it 'cause it was wireless. And we'd go you really sure you want to do this?

KARR: It used the same band of frequencies as FM radio stations so interference was an issue. It would also drift off of its frequency and cause the PA system to blast the audience with noise. Today's wireless mics are much more reliable, in part, because many of them use vacant UHF television channels with very little potential for interference. The Federal Communications Commission estimates that around 4 million wireless mics are in use nationwide at everything from kids' birthday parties to pro sports events.

(SOUNDBITE OF FOOTBALL GAME)

UNIDENTIFIED MAN: Ruling on the field is that we did have a completed pass.

KARR: The NFL can use dozens of wireless mics during a single game for officials, coaches and staff. The league is lobbying the FCC to let it keep its frequencies. It's part of a coalition that includes TV journalists, arts venues and the people behind Broadway shows.

KARR: Tom Ferrugia is in charge of government relations for the trade group the Broadway League.

FERRUGIA: When a trapdoor opens, those cue controls are being transmitted wirelessly throughout the house. All of that is seamless and happens in the background and no one's really aware of how it's done. It just seems to be magic.

KARR: That's why The Lion King, for example, uses more than a hundred wireless mics onstage and off for every performance. Broadway's worried that in order to sell off the frequencies wireless mics use now, the FCC will require users to invest in new receivers, transmitters and antennas that could cost thousands of dollars apiece and might be larger and harder to hide on performers.

FERRUGIA: The equipment that's out there now is perfect. The spectrum that we're using now is perfect for that.

KARR: Radio frequencies are not all created equal. Sound waves are similar. When I play some music...

(SOUNDBITE OF MUSIC)

KARR: If you're listening near the speakers you can hear everything, but if I step away and outside my office and close the door behind me - only the lower frequencies come through. The frequencies that wireless mics use now are like those lower frequencies - they're good at penetrating buildings. That's one of the reasons why Broadway likes them, but it's also why cellular providers want to buy them, and why others use them.

VINKO ERCEG: These frequencies are very, very important.

KARR: Vinko Erceg is a senior technical director at Brodcom - it makes wireless semi-conductor chips for a new generation of Wi-Fi transmitters and receivers that can use the microphone's frequencies. Erceg says the new devices are better than older Wi-Fi equipment because they're signals travel at least twice as far.

ERCEG: Then I can extend my range into my garden and sit there with my laptop and iPad and have this really nice range. At this point, I have very hard time receiving anything outside my home.

KARR: Those new Wi-Fi transmitters and receivers can easily move to new frequencies, but most wireless mics can't. The last time the FCC auctioned off frequencies five years ago audio engineer Rick Chinn had just bought new mics.

CHINN: Four channels, top of the pile, and it probably cost me, I don't know, two grand a channel.

KARR: After the FCC sold the frequencies, that $8,000 worth of gear was illegal to operate and it wasn't built for other frequencies. Chinn could only afford to replace two, so the other two...

CHINN: They're holding down a corner of the shelf in my shop.

KARR: Chinn says the money he lost is nothing compared to what the treasury took in from that spectrum auction - nearly $20 billion. That helped convince Congress to order the FCC to sell more frequencies. Chinn knows a thing or two about broadcast frequencies because he has a ham radio license. He worries that if the government keeps selling off frequencies, the wireless mics of the future might be as unreliable as the one he remembers from the 1970s.

CHINN: There's only so much space and we're getting crammed into it. It's kind of like living in Manhattan.

KARR: The FCC is expected to decide about wireless mics early next year. For NPR News, I'm Rick Karr in New York. Transcript provided by NPR, Copyright NPR.